Affinity maturation of NZB and BALB/cV mice anti-fluorescyl response

Immunoglobulin affinity maturation of the anti-fluorescyl response was assessed with time and compared in groups (12 weeks old) of New Zealand Black (NZB) and BALB/cV mice, following intraperitoneal immunization with 100 μg of F(I)₂₂₀ KLH per 15g of body weight. Affinity measurements were based on the quantitation of fluorescence quenching of fluorescein when specifically bound by immunoglobulin, and were expressed as relative association constants (Krs). Although Kr varied significantly within each group of mice, quantitative and qualitative differences in the pattern of affinity maturation between the two strains of mice were evident. NZB mice demonstrated a relatively more rapid increase in Kr and attained a higher average Kr for the primary response than BALB/cV mice. Thus, the NZB primary response resembled the BALB/cV secondary response kinetically and in the extent of affinity maturation. Secondary immunization of NZB mice did not result in an increase in affinity relative to the primary response. In contrast, reimmunization of BALB/cV mice produced a secondary anti-fluorescyl response of significantly higher affinity than the primary one. Comparison of affinity maturation patterns between the two mouse strains indicated a significant difference in responding lymphocyte populations. Since T_s activity in young NZB mice is known to be defective, a possible role for T_s function in the process of affinity maturation is discussed.